ITU-R M.1677-1: The Official International Morse Code Standard, Explained

Yes, Morse Code Has an Official Standard — and It Is Still in Force

Morse code is often treated as a piece of folklore, but it is formally specified by Recommendation ITU-R M.1677-1, "International Morse code." It is published by the Radiocommunication Sector of the International Telecommunication Union — the United Nations specialized agency for telecommunications. The current revision was approved in October 2009, superseding the original M.1677 of 2004. In other words, Morse code is maintained by the same body that coordinates radio spectrum and satellite orbits worldwide.

What M.1677-1 Actually Defines

The Recommendation is short, but it settles exactly what counts as valid international Morse:

• Character set: the 26 Latin letters, digits 0–9, common punctuation (period, comma, question mark, slash, parentheses and more), plus the accented é.
• Procedural signals: special signs for telegraph operations such as starting signal, wait, end of work, and error.
• Timing rules: with the dot as 1 unit — a dash is 3 units; the gap between elements inside a letter is 1 unit; between letters, 3 units; between words, 7 units.
• The distress signal: ...---... (SOS), transmitted as one continuous sign with no letter gaps.

What the Standard Deliberately Leaves Open

Interestingly, M.1677-1 specifies only the code and its rhythm — it says nothing about tone frequency or transmission speed. That is why some operators practice at 600 Hz and others at 700 Hz, and why anything from 5 to 40 WPM is equally "legal": as long as the ratios between dots, dashes and gaps are right, it is valid international Morse. Our tool defaults to a 600 Hz tone with adjustable 5–30 WPM playback, following exactly this principle.

Why a 21st-Century Standard for a 19th-Century Code

Commercial telegraphy is long gone, but Morse is still working: amateur radio operators make CW contacts across the globe, aviation VOR and NDB beacons identify themselves in Morse, and Morse-based input powers accessibility tools. Because everyone follows the same ITU document, the letter A is .- anywhere in the world, on any medium.

Our Morse code translator implements the M.1677-1 character table and timing ratios exactly — every sequence it produces would pass inspection against the official document.